The F45 8 Week Challenge – half way review

We’ve seen many exercise crazes sweep through the fitness world – HIIT, Zumba, Crossfit, Mr Motivator… the latest, the F45 gym, hails from the land of the beautiful body, Australia, and promises to deliver fitness, strength and possibly even the abs you’ve been dreaming of. We sent Katie Thomson on a journey of fitness discovery on F45’s famous 8 Week Challenge to find out just what makes these classes special and whether they are worth the hype…

I’d heard a lot about F45 gyms springing up – mostly from London-based friends who we extolling the virtues of these action-packed 45 minute sessions. When a franchise finally opened up in my home town of Bath, owned by rugby star James Haskell, I was more than intrigued to try one of these classes for myself. 

How the classes are structured:

The premise of the gym is simple – 45 minute group circuit training classes based around functional fitness – in essence, the conditioning of the muscles you need for everyday tasks like walking, sitting and standing, climbing stairs, carrying groceries etc. Each workout is designed to challenge the body and no two classes will ever be the same. This is a remarkable feat, especially if like me, you’re used to showing up to your regular gym class only to go through the motions on the bits you know you can rest on. The idea is to get in, work as hard as you physically can for 45 minutes, and you’re done – with an impressive load of calories burnt in the process. 

There’s something quite remarkable about a class that can not only work for both the super-fit and someone new to exercise, but also deliver consistent challenges. That’s the beauty of the style of workout – each session is designed to target different things, from strength, cardio vascular fitness or stability. All of them will have you sweating and gasping for air. 

F45 8 Week Challenge

The 8 Week Challenge:

Now, this is the part of F45 which has helped its cult following – you only need to have a cursory search on social media to see some of the remarkable body transformations. Free for members to participate in and also open to guest memberships, the 8 Week Challenge is an opportunity to ramp up diet and fitness efforts in order to achieve maximum fat loss during the 8 week period. 

A handy app provides a meal plan to follow, keeping you in that all-important calorie deficit and the training requirement is between 3-6 times a week. The idea is, that the functional nature of the training should help mitigate muscle loss within a low calorie diet, meaning you shed mostly fat. Overall the aim is not so much weight loss but body fat percentage loss – with losing kgs a fringe benefit. And lose kgs you will – headline stars of the plan can lose up to 16kg, but most people can expect between 4-8kg of healthy weight loss. 

Weeks 1-2

The diet plan is based around 1300 calories for women and 1800 for men, with a focus on protein for muscle recovery. The first two weeks is the most restrictive, cutting out dairy, refined sugars, red meat, gluten and alcohol. This is a form of detoxification, helping to get rid of cravings, in theory, and resetting for a healthy week ahead.

The meal plans were surprisingly delicious, and other than having to fastidiously weigh everything and coming into work laden with as much Tupperware as your average Lakeland store, I never really felt deprived. The only thing I really missed was my four cup of tea a day work comfort, replacing that with green tea. Tracking is essential to keep accountable – it’s much less tempting to reach for a sweet if you know you need to track your indiscretion on an app. My favourite is My Fitness Pal – it’s very easy to use and the barcode scanner and recipe add section are both very helpful. 

Weeks 3 – 4

So here we are at the midway point of the plan. In weeks three and four the diet plan opens up again a little to reintroduce dairy in small quantities, caffeine and red meat. Whilst I’m allowed them, my overriding desire to consume cheese in unholy quantities means that I’m generally better abstaining as you can very easily tick over that calorie limit. I’ve relaxed the plan slightly – still keeping within the calories and target macros (the ideal grams of protein, carbs and fat per day) but remaking dishes throughout the week as it makes meal prep much easier and the plan less expensive to shop for as a whole. 

I’m attending about five – six sessions a week, which sounds a lot, but is easy to fit into your schedule as they’re only 45 minutes (apart from the hour-long Saturday class, Hollywood). As with all things diet and fitness related, it’s all about how much you want the results and that will determine whether or not you make the time to do it. There are mums with four kids and stressful jobs bossing four sessions a week, so if they can make the time, so can I!

F45 Results

In results terms thus far I’ve noticed the scales shift by about 3kg and my torso, arms and legs are looking leaner and more defined. I also feel I’m getting stronger – inching toward my goal at the end of the eight weeks to be able to do a fully fledged press up! Having a Fitbit is helpful too as I’ve noticed my VO2 max has increased (that’s the maximum rate at which the heart, lungs, and muscles can effectively use oxygen during exercise – the higher it is, the fitter you are) and my resting heart rate is down by 12 beats per minute – pretty impressive stats. 


Either way, I feel like a convert and I’m almost evangelical in my descriptions of both the classes and the eating plan to friends and colleagues. Yes, I might bemoan the lack of chocolate and bread and sometimes the early starts for workouts, but for the first time in a long time I feel genuinely excited about exercising and purposeful in my food planning. The trainers are absolutely amazing too – unfailingly supportive and always on hand to answer questions and give you the boost when you want to give up. I get so turned off by ‘shouty’ instructors and the F45 approach couldn’t be further from that in its ethos – you are there to work hard and they’re there to check your form, encourage you and help you to squeeze every opportunity to improve out of a session. 

Here’s to the next four weeks – catch up with us then for my full results!

Katie trains at the F45 Bath gym. Find out more at